The aims of this Core are to: Undertake strategic comparisons between New York City data and other key locations, nationally and internationally to: 1. Provide information on the applicability of findings regarding high- risk groups from the NYC epidemic to other locations; 2. Provide projects with opportunities to assess the generalizability of their findings in other locations and to undertake multi-site investigations; 3. Develop knowledge regarding the AIDS epidemic at the community-wide level of analysis (utilizing the NY epidemic as the unit of analysis).